When a living body, such as a human patient, is sick, being operated upon or undergoing sleep studies, it is often necessary to monitor air flow and in some cases to supplement the body's inhalation with a treating gas, such as oxygen or a gaseous anesthetic. In these instances, an accurate quantitative determination of the amount of at least one gaseous component, such as carbon dioxide, in the blood passing through the pulmonary alveoli of the living body is highly desirable. In addition, it is also desirable to have an accurate quantitative determination of the amount of air the patient is breathing. In intensive care situations or under a regional or general anesthetic, an accurate determination of the composition of the breathing gas in the pulmonary alveoli allows the bodily functions of a patient to be more readily supervised and treatment of the patient more favorably adapted to the state of those functions. Accurate measurements of at least one gaseous component in the exhalation of a living body also may help improve related diagnostic methods for determining bodily conditions. Measuring the concentration of at least one gaseous component in exhaled breathing gas may be conducted continuously to provide relatively short response times and to enable rapid alterations in an ongoing medical procedure, thereby preventing adverse effects or damage to the living body. One area of particular interest is the monitoring of end-tidal carbon dioxide, which is the partial pressure of the carbon dioxide component of exhaled gas at the end of exhalation in a spontaneously breathing patient. The quantitative monitoring of end-tidal carbon dioxide in spontaneously breathing patients who are unintubated (those not requiring intubation with an endotracheal tube) would be particularly useful for those unintubated patients who while awake are being treated with supplemental oxygen administration and are receiving regional or local anesthesia or are in a recovery room during emergence from residual general anesthesia.
Another area of concern is the use of cannulas on pediatric patients. The practice during pediatric sleep studies has been increasingly trending toward the measurement of end-tidal CO2 to ascertain the respiratory status of the pediatric patient. With the advent of nasal pressure monitoring for events of sleep apnea, the need for dual cannula capability has increased with pediatric patients that find two cannulas taped together cumbersome.
Yet another area of concern is accurately measuring the exhaled gases in a patient with a blocked nostril. Prior art such as a cannula which diverts gases from one nostril to one measuring device and gases from another nostril to another measuring device will provide inaccurate results if the patient has a single blocked nostril. U.S. Pat. No. 5,335,656 issued to Bowe, is a cannula with two nasal tubes. However this patent is directed to nasal tubes connected to a single narrow tube with a wall which partitions the hollow body.
U.S. Pat. No. 6,938,619 issued to Hickle is a mask free oxygen delivery and gas sampling system. However, the invention inserts two tubes in one nostril and no tubes in the patient's other nostril.
U.S. Pat. No. 4,989,599 issued to Carter is a cannula enclosed within another cannula. However, this patent does not have a hollow body to allow mixing of the gases from two nostrils.
U.S. Pat. No. 6,439,234 issued to Curti is a nasal cannula. However, the hollow body has a wall separating the hollow body into compartments.
U.S. Pat. No. 5,046,491 issued to Derrick is an apparatus to collect nasal and oral gases. However, the oral gas hood is used to collect oral gases and not as a mixing chamber to mix nasal and oral gases.
There is therefore a real need in the art for a multipurpose cannula that is small enough to be comfortable in a patient's nostrils yet be capable of measuring several variables and/or delivering a treating gas to a patient, even if the patient has a blocked nostril. One such example is that there is a need for an apparatus having the combined advantageous of insufflating a treating gas into the patient and sampling and analyzing a portion of the patient's exhaled breathing gas. Moreover, there is a real need in the art for simultaneously sampling and analyzing a portion of the patient's exhaled breathing gas and measuring the patient's airflow or simultaneously measuring a patient's airflow. Moreover, there is a real need for a cannula that would allow the accurate measurement of a patient's exhaled gases and insufflating a treating gas from patients with a blocked nostril.